My 90 days is up, can I do a visa run to Mae Sai? or better for me can I extend for another 90 days at chiang mai immigration? I heard border runs were out at Mae Sai and I'm pretty sure I extended my visa for 90 days at immigration before for B1900. 

If you have a multiple entry non-o visa you can leave and re-enter the country to get a new 90 day entry at Mae Sai.

If married to or the parent of a Thai you can apply for a 60 day extension at immigration to visit them.

Thanks udonjoe! Most helpful.